3D scanning has helped a team of researchers from the Salk Institute for Biological Studies uncover some interesting things about how plants grow. Specifically, the technology enabled them to discover that plants grow in a very similar manner to human brain cells.

The research project, recently published in the journal Current Biology, relied on data obtained through 3D laser scanners. The findings suggest that various “branching growth” biological systems could be governed by universal rules of logic.

Saket Navlakha, an assistant professor at Salk’s Center for Integrative Biology and a senior of the study, explained: “Our project was motivated by the question of whether, despite all the diversity we see in plant forms, there is some form or structure they all share. We discovered that there is—and, surprisingly, the variation in how branches are distributed in space can be described mathematically by something called a Gaussian function, which is also known as a bell curve.”

The project was born from the question of whether different plant forms are determined by some “unseen organizing principle.” That is, while plants grow in many different ways in order to overcome environmental challenges, the researchers wondered if perhaps there was some sort of uniform pattern to their growth that could be discerned.

To gain some insight into this, the researchers used a high-precision 3D scanner to “measure the architecture of young plants over time” and to quantify their growth to be mathematically analyzed. For the project, three plant species were used: sorghum, tomato, and tobacco.

Plants use the same rules to grow under various different conditions

(Image: Salk Institute​)

For the experiment, the researchers grew the three plants from seeds and exposed them to varying lighting and temperature conditions (similar to ones they might undergo naturally). Once every few days, for a period of a month, researcher Adam Conn (the study’s first author) 3D scanned each plant. By the time the experiment was done, Conn had reportedly scanned nearly 600 plants.

The 3D scans allowed the researchers to visualize in detail the architectures of the plants as they grew, which included how growing branches became distributed in space. Using a digital point cloud of each stage of each plant, the research team was able to generate a statistical description of “possible plant shapes" by studying the plant’s "branch density function.”

The analysis of the 3D scans showed three main growth properties: separability, which means that growth in one direction is independent of growth in others; self-similarity, which means that all the plants had the same underlying shape; and a Gaussian branch density function, which means that despite the different plant species or environmental conditions, the branch density data was governed by a “Gaussian distribution that is truncated at the boundary of the plant."

Researchers Adam Conn and Saket Navlakha

(Image: Salk Institute​)

In other words, the branch growth of the plants was found to be densest at the plant’s center and becoming less dense the farther out it got—following a bell curve pattern. These results showed a level of evolutionary efficiency that even the researchers were surprised by. The team says its properties could lead to more research, especially in the field of genetically engineered crops.

So, how does this study relate to the human brain? Well, according to research done by Charles Stevens, a professor in Salk’s Molecular Neurobiology Laboratory and a researcher on the plant study, he found the same three mathematical properties in brain neuron growth.

He says, “The similarity between neuronal arbors and plant shoots is quite striking, and it seems like there must be an underlying reason. Probably, they both need to cover a territory as completely as possible but in a very sparse way so they don’t interfere with each other.”

The 3D scanning research project was realized with funding from the Howard Hughes Medical Institute (HHMI), the National Institutes of Health, the National Science Foundation, and a Salk Innovation Grant.